Problem Solving and Program Design

COMP104 Problem Solving / Slide 2 Our First Program // a simple program #include using namespace std; int main() { cout << "Hello world!" << endl; return 0; } Preprocessor statements Print statement Ends execution of main() which ends program Comments Function Function named main() indicates start of program

COMP104 Problem Solving / Slide 3 C++ Software Development * Major activities Editing (to write the program) Compiling (creates.obj file) Linking with compiled files (creates.exe file)  Object files  Library modules Loading and executing Testing the program

COMP104 Problem Solving / Slide 4 Problem Solving * Define the problem. * Develop a solution. n Outline solution first. n Then write down the solution steps in detail. * Test the solution and revise if necessary. * Document and maintain the solution.

COMP104 Problem Solving / Slide 5 Example 1 * Define Problem: n Find the best way to travel from HKUST to Central quickly and cheaply.

COMP104 Problem Solving / Slide 6 Example 1 * Develop Solution: n Evaluate all possible routes and modes of transportation n Select the route that meets our goal (fastest and cheapest)

COMP104 Problem Solving / Slide 7 Example 1 * Testing: n Test the route and make sure conditions have not changed (e.g., increased bus fares, road construction). * Documentation: n Give description of solution and explain it. * Maintenance: n Test and revise the route as needed.

COMP104 Problem Solving / Slide 8 Programming as Problem Solving * Define the problem. n What is the input & output? n What constraints must be satisfied? n What information is essential? * Develop a solution n Construct an algorithm (steps that must be done) n Implement a program. * Compile, test, and debug the program. * Document and maintain the program.

COMP104 Problem Solving / Slide 9 Example 2 * Problem Statement: n Convert US dollars into Hong Kong dollars. * Problem Analysis: n Input: Amount in US$ n Output: Amount in HK$ n Apply official currency exchange rates.

COMP104 Problem Solving / Slide 10 Example 2 * Algorithm n Read in amount in US$ n Calculate the HK$ amount n Display the results

COMP104 Problem Solving / Slide 11 Example 2 // converts US$ to HK$ #include using namespace std; int main(){ double usdollars; double hkdollars; // read in amount in US$ cout <<"Enter US$ amount and press return: "; cin >> usdollars; // calculate the HK$ amount hkdollars = 7.8 * usdollars; // display the results cout << "US$" << usdollars << " = HK$" << hkdollars << endl; return 0; }

COMP104 Problem Solving / Slide 12 Example 2 * Program Implementation: Program comments: // Library reference: #include Function type: int Function name and (lack of) parameters: main( ) Statement braces: { } Variable declaration: double Input/output functions: cin, cout

COMP104 Problem Solving / Slide 13 What Makes a Good Program? * Correctness n Meets the problem requirements n Produces correct results * Easy to read and understand * Easy to modify * Easy to debug * Efficient n Fast n Requires less memory